Many ingredients or natural foods do not originally have a particular odor, perfume or fragrance, but develop it only through heat treatments or fermentation reactions, such as those to which fruits, pods, seeds and leaves are subjected.
These treatments induce a series of biochemical transformations within the plant structure, which lead to the development of molecules with the characteristic smell and aroma that we recognize.
In this article we will find out how the aromas of vanilla, cocoa and coffee are obtained, which are among the main aromas and natural products that we consume daily in food.
Vanilla is the most popular food aroma used as an additive to "enhance" food preparations today. It is found in a multitude of food products, especially in pastries, drinks and ice cream. Vanilla beans are produced from the flower of a tropical orchid, Vanilla planifolia. This orchid must go through a precise and lengthy production process to be shaped into the stick and aroma we find at the market.
The plant matures and begins to bloom after about a year and a half from its planting; once fertilized, the flower withers rapidly and begins to grow a green pod which develops in 9 months and is finally harvested when its size reaches around 30 cm. These pods do not yet have the characteristic aroma of vanilla, but will undergo a long and complex treatment, which will transform them both in color and aroma.
The treatment consists of 4 stages:
Killing: the pods are immersed in water at 60-80° C (140-175° F) for a few minutes, this rapid heat treatment induces the fermentation of the sugars contained in the pod pulp.
Sweating: After "killing" the pod, it is necessary to "sweat" it, that is, control the humidity emitted during fermentation which could cause the formation of mold and bacteria in the subsequent stages of processing. This phase lasts 7-10 days and in this period of time vanillin and many other molecules begin to be produced so that the aroma of vanilla begins to form, while the pod slowly changes from green to dark brown.
Drying: the pod must be dried under controlled conditions and during this process it will lose 70% of its initial weight.
Conditioning or maturation: In this last phase, the now black pods are placed in crates and left to rest for several months in well-ventilated rooms, allowing the formation of the whole range of vanilla aromas to be completed.
Sensory quality and aroma composition
Finally, the ripe vanilla pods pass through quality control, where they are separated and collected in small bundles of 30-40 sticks based on the length, thickness and above all, aroma. For the latter factor, a sensory analysis is carried out, during which the bundle of sticks is opened in the center and carefully smelled by experts, generally only women.
The aroma of vanilla is mainly made up of vanillin, which is the most abundant aromatic compound (~ 2% of the total weight of the pod); other important chemical components with a lower concentration (0.001-0.02%) are para-hydroxybenzaldehyde (sweet-biscuit odor), para-hydroxybenzyl alcohol (sweet-floral odor), guaiacolo (smoky smell), methyl guaiacolo (spicy woody odor), cresol (balsamic odor), isobutyric acid (butter odor), 2-3 butanediol (floral odor), eptenal (fatty odor).
Cocoa is the basic raw material of one of the best-loved foods in the world and that few don't like: chocolate. But, before becoming the glutton that we know well, it is necessary that the cocoa beans (see cover photo), from which the chocolate takes shape, taste and aroma, are treated, according to a precise procedure. This provides the master chocolatiers with the best raw material.
Theobroma cacao is a small tree native to South America which is also grown in the tropical areas of central Africa. The most widely used botanical varieties are Forastero (70% of the total world cocoa production), Criollo (15%) and Trinitario, a natural hybrid between Forastero and Criollo. The final aroma of the product, cocoa paste, strictly depends on the quality of the beans produced by the tree and on their production process, from harvest to the final grinding.
The stages of production:
Fermentation: The fruit of Theobroma cacao, called cabosse, have a shape reminiscent of large pine cones and inside, mixed in a gelatinous pulp, they contain about 15-20 precious seeds, the cocoa beans. Once extracted from the cabossa, the beans and the cocoa pulp are placed in crates or baskets where, protected from light, they are left to rest for about a week: during this period a series of fermentative reactions begin, during which they begin to develop all the precursors of the cocoa aromas.
Drying: The beans are then dried, which reduces their humidity by up to 6-7%, blocking the fermentation which, if prolonged further, would damage the quality of the final cocoa paste. Drying in the sun guarantees a better quality than using temperature-controlled ovens.
Roasting: Roasting the beans is the most important phase of the process, the one on which all the characteristic aromas of cocoa depend: generally the roasting lasts from 30 to 120 minutes at a temperature between 100 and 130° C (210-260° F).
Grinding: The toasted and fragrant beans are then crushed, initially into medium-sized pieces to obtain the so-called cocoa grain or grits. This is then finely ground through a series of consecutive temperature-controlled cylinders which, by melting the fat contained in the beans, transform the ground material into a fluid mass called cocoa paste which will become the raw material for the production of chocolate.
The chemistry of the cocoa aroma
The aroma of cocoa is due to several hundred chemical molecules that develop during the fermentation and roasting phases of the cocoa beans: especially in roasting, the high temperature causes the so-called Maillard reaction between amino acids to develop and the sugars present themselves in the structure of the beans. This reaction leads to the formation of all volatile molecules which then develop the typical olfactory profile described by expert sensory analysts as aromatic, toasted, smoky, woody, earthy, malty, vanilla, floral, fruity.
Among the main chemical molecules that we find in the aroma of cocoa there are alcohols such as benzyl alcohol, butanol, ethanol, acids such as phenylacetic acid and esters such as ethyl acetate and benzyl acetate: all of these molecules participate in the floral smell that is often found in cocoa. Its sweet and fat fruity odors are due to the presence of aldehydes such as butanal, phenylacetaldehyde, benzaldehyde and to ketones such as diacetyl and acetophenone. Finally the methoxy pyrazines and the phenols (guaiacolo) constitute the toasted / tobacco / earthy odors.
The aroma of coffee is most likely one of our most intense olfactory memories, an odor that we immediately recognize in the midst of a thousand others. It represents the moments and places of our daily habits, such as waking up, breakfast, the coffee bar, the break at work, the chat with friends.
The coffee tree with its precious drupes (coffee fruit which typically encase two coffee beans) is native to Ethiopia. Arab culture has made extensive use of coffee in the form of drink for centuries, and in the 16th century, it also reached Europe through trade routes; initially treated as an oriental curiosity, the consumption of coffee spread in the 1700s from Venice, which started offering the famous coffee drink at bars, and consumed all over the world today. Caffè Florian, one such coffee bar, is still in business today.
In the eighteenth century, coffee had conquered the tastes of people throughout the western world and also spread to the Americas, to the point that the quantities produced in North Africa were no longer sufficient to satisfy their demand and the cultivation of coffee was thus exported to Central and South America by Dutch traders. Today 70% of world coffee production is in South America. Brazil is the main world producer, followed by Colombia, Guatemala and Mexico. 10% of world coffee production is in central Africa, where the main producers are Angola, Ivory Coast, Ethiopia and Uganda, and the remaining 20%, is in Indonesia and India.
Many species of plants of the genus Coffea are known, but only two have economic importance: Coffea Arabica and Coffea Canephora, the latter more commonly known as Robusta. From the Arabica variety you get an arguably tastier, more aromatic coffee with a less bitter and more persistent taste and it represents 3/4 of the world production; the Robusta variety constitutes the remaining quarter of the production, with a full-bodied and bitter taste but with a weaker aroma and, is therefore, considered of a lower quality.
The ground, roasted bean whose taste and aroma we appreciate so much is far from what coffee looks like at the beginning of its transformation. Coffee requires a long manufacturing process before arriving in our daily cup.
When ripe, the drupe is red and inside there is a waxy pulp and two seeds placed one in front of the other, wrapped in a rigid and thick film that protects them.
Collection, drying, sieving and shipment of raw beans
The collection of drupes is performed by manual or mechanical techniques. The final quality of the product depends very much on the harvesting technique used: generally manual harvesting is better, however it is the least used, due to the very high costs. From the drupes the shell is eliminated and then the coffee beans are freed from their external film and left to dry in the sun. The beans are then sieved, divided by size, and packed and shipped to roasted coffee producers all over the world for the final production stages, which will give life to coffee as we know it.
Mixing and roasting
To obtain its unique taste and aroma, the different types of coffee are first mixed in the proportions established by each producer: these recipes produce the precise "blend", the percentage composition of the different types of coffee which will then be roasted, and which diversify the products from those of different coffee brands on the market. The roasting, then puts the definitive sensorial stamp on the product that will be packaged; this phase is of fundamental importance since it is here that the bean is transformed into the coffee we love so much and where the aroma develops concretely. The roasting is carried out at a temperature between 200° and 230° C (390-445° F) in just 10 to 15 minutes where the toasting thermal profiles and the contact times are strictly controlled, to avoid the appearance of spurious odors or defects that would lower the quality of the coffee product; these operating conditions also have a very evident impact on the physical properties of coffee beans which lose up to 20% of their residual moisture, increase in volume due to the development of carbon dioxide and change color, going from green to light brown until they arrive, finally, to darker shades.
The roasted coffee is then ground in different types of grain size with respect to the type of market they will be sold in.
What makes the aroma of coffee so recognizable is its complex chemical composition, but above all, it is the fundamental presence of sulfur compounds called thiols which give the characteristic hint of toasted that we expect from the product. As is the case with cocoa production, the Maillard reaction is present in coffee roasting, leading to the development of a complex series of mixtures of volatile chemical molecules which, in addition to the aforementioned thiols, will form the unmistakable spectrum of the coffee aroma described as toasted, aromatic, pungent, bitter, spicy, fruity, earthy. Fatty odors are due to aldehydes and ketones such as anisaldehyde and exanal and diacetyl, the earthy smells are due to octyl alcohol, the toasty smell is due to furfurylthiol, while the smells of smoked and roasted are due to alkyl pyrazines and guaiacolo, and the spicy and caramel notes are due to furans.